Uniparental isodisomy of chromosome 2 causing MRPL44-related multisystem mitochondrial disease

Mutations in nuclear-encoded protein subunits of the mitochondrial ribosome are an increasingly recognised cause of oxidative phosphorylation system (OXPHOS) disorders. Among them, mutations in the MRPL44 gene, encoding a structural protein of the large subunit of the mitochondrial ribosome, have been identified in four patients with OXPHOS defects and early-onset hypertrophic cardiomyopathy with or without additional clinical features. A 23-year-old individual with cardiac and skeletal myopathy, neurological involvement, and combined deficiency of OXPHOS complexes in skeletal muscle was clinically and genetically investigated. Analysis of whole-exome sequencing data revealed a homozygous mutation in MRPL44 (c.467 T?>?G), which was not present in the biological father, and a region of homozygosity involving most of chromosome 2, raising the possibility of uniparental disomy. Short-tandem repeat and genome-wide SNP microarray analyses of the family trio confirmed complete maternal uniparental isodisomy of chromosome 2. Mitochondrial ribosome assembly and mitochondrial translation were assessed in patient derived-fibroblasts. These studies confirmed that c.467 T?>?G affects the stability or assembly of the large subunit of the mitochondrial ribosome, leading to impaired mitochondrial protein synthesis and decreased levels of multiple OXPHOS components. This study provides evidence of complete maternal uniparental isodisomy of chromosome 2 in a patient with MRPL44-related disease, and confirms that MRLP44 mutations cause a mitochondrial translation defect that may present as a multisystem disorder with neurological involvement.

     

Detection and quantification of mitochondrial DNA deletions in individual cells by real-time PCR

Defects of mitochondrial DNA (mtDNA) are an important cause of disease and play a role in the ageing process. There are multiple copies of the mitochondrial genome in a single cell. In many patients with acquired or inherited mtDNA mutations, there exists a mixture of mutated and wild type genomes (termed heteroplasmy) within individual cells. As a biochemical and clinical defect is only observed when there are high levels of mutated mtDNA, a crucial investigation is to determine the level of heteroplasmic mutations within tissues and individual cells. We have developed an assay to determine the relative amount of deleted mtDNA using real-time fluorescence PCR. This assay detects the vast majority of deleted molecules, thus eliminating the need to develop specific probes. We have demonstrated an excellent correlation with other techniques (Southern blotting and three- primer competitive PCR), and have shown this technique to be sensitive to quantify the level of deleted mtDNA molecules in individual cells. Finally, we have used this assay to investigate patients with mitochondrial disease and shown in individual skeletal muscle fibres that there exist different patterns of abnormalities between patients with single or multiple mtDNA deletions. We believe that this technique has significant advantages over other methods to quantify deleted mtDNA and, employed alongside our method to sequence the mitochondrial genome from single cells, will further our understanding of the role of mtDNA mutations in human disease and ageing.     

云南10个民族红细胞酸性磷酸酶型分布调查

用淀粉凝胶电泳法对云南省汉族及9个少数民族的红细胞酸性磷酸酶(ACP_1)的表型分布进行了调查,检出A、BA和B3种表型,计算得云南汉、彝、白、傣、瑶、佤、哈尼、布朗、基诺和拉祜族ACP_1~A、ACP_1~B的基因频率依次为0.2067、0.7933;0.2406、0.7594;0.2341、0.7659;0.3750、0.6250;0.2300、0.7700;0.2727、0.7273;0.3594、0.6406;0.3036、0.6964;0.2381、0.76119和0.4474、0.5526。未发现ACP_1~C基因及其它稀有基因。研究表明,ACP_1表型的分布存在着一定的种族与民族差异。     

云南省15个民族红细胞PGM1亚型分布调查

采用超薄层聚丙烯酰胺凝胶等电聚焦电永地,对云南省汉族、彝族、白族、苦聪人、哈尼族、傣族、瑶族、基诺族、布郎族、瓦族、拉祜族、回、傈僳族、纳西族和普米族等１５个民族红细胞ＰＧＭ１亚型分布进行了调查。计算出上述１５个民族的ＰＧＭ１亚型分布的基因频率及ＤＰ值,经统计学检验表明：ＰＧＭ１亚型的分布上述１５个民族中存在着明显的民族间差异,但在北京、辽宁、西安、云南４个不同地区的汉族人群中ＰＧＭ１型分布却无显     

Long non‐coding RNA TNRC6C‐AS1 promotes methylation of STK4 to inhibit thyroid carcinoma cell apoptosis and autophagy via Hippo signalling pathway

The role of long non‐coding RNAs (lncRNAs) in thyroid carcinoma (TC), the most frequent endocrine malignancy, has been extensively examined. This study investigated effect of interaction among lncRNA TNRC6C‐AS1, serine/threonine‐protein kinase 4 (STK4) and Hippo signalling pathway on TC. Initially, lncRNA TNRC6C‐AS1 expression in TC tissues was detected. To explore roles of lncRNA TNRC6C‐AS1, STK4 and Hippo signalling pathway in TC progression, their expressions were altered. Interaction between lncRNA TNRC6C‐AS1 and STK4, STK4 promoter methylation, or Hippo signalling pathway was verified. After that, a series of experiments were employed to evaluate in vitro ability of apoptosis, proliferation and autophagy of TC cells and in vivo tumorigenicity, and tumour growth of TC cells. lncRNA TNRC6C‐AS1 was highly expressed while STK4 was poorly expressed in TC tissues. LncRNA TNRC6C‐AS1 promoted the STK4 methylation and down‐regulated STK4 expression, which further activated the Hippo signalling pathway. STK4 silencing was observed to promote the proliferation ability of TC cells, inhibit the apoptosis and autophagy abilities, as well as enhance the tumorigenicity and tumour growth. Moreover, the in vitro proliferation ability as well as the in vivo tumorigenicity and tumour growth of TC cells were inhibited after the blockade of Hippo signalling pathway, while the apoptosis and autophagy abilities were promoted. The results demonstrate that the lncRNA TNRC6C‐AS1 increases STK4 promoter methylation to down‐regulate STK4 expression, thereby promoting the development of TC through activation of Hippo signalling pathway. It highlights that lncRNA TNRC6C‐AS1 may be a novel therapeutic target for the treatment of TC.     

Differences in RNA processing underlie the tissue specific phenotype of ISCU myopathy

Hereditary myopathy with lactic acidosis, or myopathy with exercise intolerance, Swedish type (OMIM #255125) is caused by mutations in the iron–sulfur cluster scaffold (ISCU) gene. The g.7044G > C ISCU mutation induces a splicing error in the pre-mRNA that strengthens a weak intronic splice site leading to inclusion of a new exon and subsequent loss of mRNA and protein. While ISCU is widely expressed, homozygosity for this particular intronic mutation gives rise to a pure myopathy. In order to investigate tissue specificity and disease mechanism, we studied muscle, myoblasts, fibroblasts and blood cells from the first non-Swedish case of this disease. Consistent with the recognised role of ISCU, we found abnormal activities of respiratory chain complexes containing iron–sulfur clusters in patient muscle. We confirmed that, in the presence of the g.7044G > C mutation, splicing produces both abnormally and normally spliced mRNA in all tissues. The ratio of these products varies dramatically between tissues, being most abnormal in mature skeletal muscle that also has the lowest relative starting levels of ISCU mRNA compared with other tissues. Myoblasts and fibroblasts have more of the normally spliced variant as well as higher starting levels of ISCU mRNA. Up-regulation of mtDNA copy number was found in skeletal muscle and myoblasts, but not fibroblasts, and is thought to represent a compensatory response. Tissue specificity in this disorder appears therefore to be dependent on the mRNA starting level, the amount of remaining normally spliced RNA, and the degree to which compensatory mechanisms can respond.     

Assessment of Heavy Metal Contamination in the Surrounding Soils and Surface Sediments in Xiawangang River,Qingshuitang District

Xiawanggang River region is considered to be one of the most polluted areas in China due to its huge amount discharge of pollutants and accumulation for years. As it is one branch of Xiang River and the area downstream is Changsha city, the capital of Hunan Province, the ecological niche of Xiawangang River is very important. The pollution treatment in this area was emphasized in the Twelfth Five-Year Plan of Chinese government for Xiang River Water Environmental Pollution Control. In order to assess the heavy metal pollution and provide the base information in this region for The Twelfth Five-Year Plan, contents and fractions of four heavy metals (Cd, Cu, Pb and Zn) covering both sediments and soils were analyzed to study their contamination state. Three different indexes were applied to assess the pollution extent. The results showed this area was severely polluted by the four heavy metals, and the total concentrations exceeded the Chinese environmental quality standard for soil, grade III, especially for Cd. Moreover, Cd, rated as being in high risk, had a high mobility as its great contents of exchangeable and carbonates fractions in spite of its relative low content. Regression analysis revealed clay could well explain the regression equation for Cd, Cu and Zn while pH and sand could significantly interpret the regression equation for Pb. Moreover, there was a significant correlation between Non-residual fraction and I_geo for all the four metals. Correlation analysis showed four metals maybe had similar pollution sources.